When an airline customer orders a commercial aircraft from a manufacturer, many details are generally customized for the ordering customer. These details include the layout of the passenger compartment. Generally known as the “layout of passenger accommodations” (“LOPA”), the placement of seats, bulkheads, galleys, and lavatories vary from customer to customer in accord with the customer's corporate identity. One customer or commercial carrier may choose to emphasize the amount of leg room offered in coach class while another may choose to add a row of seats and gain efficiencies in terms of numbers of passengers per flight.
The LOPA is part of the order and is generally accommodated by the manufacturer. The customer or commercial carrier will designate a seat manufacturer and model line. The LOPA accompanying the order is drawn to include locations of various seats throughout the cabin. Thus, the LOPA becomes a part of the contract specification, requiring fulfillment in order to complete the order. Generally, the LOPA is provided to the manufacturer in the form of a plan view drawing, either in paper or in electronic form. Alternatively, the LOPA could exist as a database filled with numbers descriptive of precise seat anchoring locations and the seat parts anchored thereto. By either means, the customer's desires as to the precise seat placement are communicated to the manufacturer with the intent that the manufacturer build out the passenger cabin appropriately.
The FAA has directives that require that a passenger seat be designed to carry a designated weight through a designated acceleration along a number of designated axes without parting from or distorting the floor plate to which the seats are affixed. The regimen that has been traditionally used to solve the problem is to define each seat load and seat weight as a mass at a center of gravity on a lever arm exerting a force on fasteners affixing the seats to the floor plate. For a single engineer, the process requires the grouping of seats into units by seating capacity, size, attachment angle, etc.; calculating the response of the unit to acceleration; distributing the resultant force among the fasteners; cumulating the results for all of the units; compiling the results into a template; and verifying the results as sensible. The process currently requires between 180 and 250 hours to generate a compiled result.
There exists then, an unmet need in the art for an inexpensive and accurate way to calculate stresses on a floor plate resulting from the acceleration of passenger loads in seats placed according to a LOPA defining a passenger cabin.